Polyphase electric furnace.



l. L. DIXON.

POLYPHASE ELECTRlC FURNACE.

APPLICATION mm JUNE 26.1911.

1,241,499. Patented 00:. 2, 1917.

7 g Lg flttokmuf JOSEPH L. DIXON, 0F DETROIT, MICHIGAN.

POLYPHASE ELECTRIC FURNACE.

Specification oi Letters Patent.

Patented oct. 2, 1917.

Application filed lune 28, 1917. Serial No. 176,971.

To all whom it may concern:

Be it known that I, Josnrn L. DIXON, a subject of the King of Great Britain, residing at Detroit, county of W'ayne, and State of Michigan, have invented certain new and useful Improvements in Polyphase Electric Furnaces, of which the following is a full, clear, and exact description.

The invention, subjectofthis application, pertains to polyphase electric furnaces, and it has for its object the provision of new and improved means for effecting their regulations.

The apparatus heretofore used for this purpose consists, generally speaking, of current transformers which supply current to solenoids that operate contact making devices which control the rotation of motors in opposite. directions and thus raise or lower the electrodes. In this way any deviation from the desired value of the current in any one of the electrodes is supposed to cause the electric motor to so operate as to move the electrode in a direction tending to bring the current back to the desired value.

In actual practice, however, such apparatus gives rise to very imperfect regulation of the electrodes. Let it be assumed, for example, in the case of a 3-phase furnace with three upper electrodes arcing into the bath, that when each electrode is carrying the desired current of 1000 amperes the arc gap between each electrode and the bath is one inch. Then, should one of the electrodes come into actual contact with the hath, notonly that particular one, but also the other two electrodes will carry an excessive current. Such current will cause the regulating apparatus to raise not only-the electrode which is touching the bath, but also the other two which maybe correctly located with relation to the bath.

The improvements which I have devised' have for their immediate purpose the overcoming of this objection or defect, and to regulate each electrode, not directly and entirely in accordance with any excess or deficiency of current in that particular electrode, but that each of the latter shall be adjusted at such time, and at such time only, as it may be incorrectly located with respect -to the bath.

Themeans which I employ for the accomplishment of this result are shown in the accompanying drawing, in Which- Figure 1 a diagrammatic illustration of Fi 1 representsan electricfurnace bath D, with three electrodes, A, B, C, arcing into the same and connected with and supplied by current from the coils of-a three-phase source E. In each of the supply circuits is a transformer F, G, H, the circuit of the first named including a solenoid K, and

those of the other two a solenoid L, which a they cohjointly energize.

The two solenoids K, L, are mechanicallv opposed to each other through a beam M,

pivoted at N. At one end of this beam is a contact 0 which, when the'beam is shifted from a horizontal position, engages either an upper conductin stop P or a lower conducting stop Q; W hen engaging the firstnamed stop P the contact 0 com letes the circuit of an electric motor R and drives it in a direction to raise the electrode C. On the other hand, when the'lower stop Q is enga cd the motor is reversely rotated and there liy lowers the electrode C.

It may be assumed that the transformer F has a ratio of 1000 to 1.73, so that when 1000 amperes of current flow through the electrode C, the solenoidK will be energized by a current of 1.73 amperes. This solenoid has 100 turns.

The "transformers G, H are connected with the solenoid L, and the secondary terminals of onea're reversed so that the vectors o'fthe secondary feurrents are not inclined to each other at an angle of 120, but at an angle of 60; In this way, when each of the trans- I formers G, H delivers a current of 1.73 am peres, the resultant current energizin the solenoid will be t; amperes. The ratio of each of the transformers G, H is 1000 to 1.73, and the solenoid is so constructed that when the electrodes A and B are each carrying 1000 amperes, the magnetic resultant of the solenoid is 108 ampere turns, so that'it has 36'turns. 1

When each of the electrodes A, B, C is carrying the desired current of,,tiy, 1000 amperes, then the solenoid K tends to lift its end of the beam M witlna force 'resulting from 172+ ampere turns while the solenoid L tends to lift its end of the beam with a force resulting from 108 ampere turns. The first named solenoid therefore exerts a pull in excess of that exerted by the other equivalent to G5 ampere turns. To counteract this excess and maintain, the beam in balanced position, a spring or a weight S is attached to the beam under the solenoid K which opposes tho-upward'pull of the latter. It is manifest that the beam M will remain in its balanced position whatever currents Ina bc energizing the two solenoids, providiid those are'in such proportion that the solenoid K exerts a. pull equivalent to 63' ampere turns in excess of that of the solenoid In order now to more readily understand the operation of the apparatus, the currents flowing in the electrodes and the solenoids will be graphically analyzed into their coinponcnts. Thus, the. current flowing in electrodes C consists of two components, one being the current passing between electrodes B and C, and the other that passing between electrodes A and C. These components may be represented by vectors at 60 from each other, and when the system is balanced and each electrode is carrying 1000 amperes, each component consists of a current 1000/ 1.73 or approximately 580 ainperes. Similarly, the currents in the electrodes A and B each consists of t "'0 components differing in phase by 00, each being approximately 580 ampores. In like manner the current delivered by. the transformer F may be analyzed into two components differing in phase by 60". lVhen the system is balanced and each electrode is carrying 1000 amp'eres, the transformer" l" isdclirermg a current of 1.73 amperes,

the two component currents each beingi one ampere, and each bcmgderivei *rorh the corresponding component currcntcf 5S0 aniperes flowing in the electrode 0. This from the currentsplitting of the current from transformerl" into its components is shown in the vector diagram Fig. 2, which will be readily understood to represent byC, 13; the component derived from the current passing between electrodes C and B, and by L, A that derived passing between electrodes C and A.

Similarly the vector diagram, Fig. 3, illustrates the cllli'Ell; which energizes the sole noid L. split into its components, the several vectors representing the current derived from those passing between the various pairs of electrodes.

Assuming now a constant dbltage applied to the electrodes A, B, and C, then the amount of current flowing into the furnace will depend upon the resistance of the arcs between the electrodes and the bath, and assuming further that the furnace is operating with the three arcs ofthe same and such- A and B decreases to one-half of its normal 7 value, while as a co notice the current passingbetween these e ectrodes increases to twice its normal value. For'the same reasons the current passing between B and 0.

becomes of twice its normal value, while that between A and 0 remains normal.- Referring again to the vector dia it will he observed that when the vectors A B and B C are each increased to twice.

normal value; the current energizing the solenoid K increases-from 1.73 to 2.65 am pores, and the pull of this solenoid'is now the result of 265 ampere turns. The current energizing the solenoid L, on the other hand, increases from three to approximately 5.57 ampeies, and-the pull know the result of approximately 200.5 ampere turns.

The solenoid K, however, still exerts-a pull on the beam in excess of that exerted by the solenoid L, equivalent to 64.5 ampere turns, but as the original excess was 65' ampere turns, the difference of .5 of an am pore turn is negligible and not 'sujlicient to materially affect t e balance of the beam M and therefore the electrode 0 is not i by theiorm oi regulating as it would be apparatus usually employed. 1

Again, and as another illustration, should the electrode B become withdrawn to such an extent from the bath that no current pauses through it, then the only current entering the bath is that (passing between the two electrodes A and In this case the current energizing such of the solenoids K and L is one ampere. Therefore, the excess pull of solenoid K over that which solenoid L exerts, becomes the equivalent of ampere turns instead of theoriginal'65am inc,

turns. This diflerence is not. suflicent to disturb the balance of the beam, and hence the electrode 0 will not be lowered as it would.

be by the ordinary meansof regulation emp10 ed.-

n a like manner, any increase or d of the current through the electrode 0, re-

sulting from a variation'ofthe resistance of the are between electrode at and; the bath, will have no eifect or lowerin 5 of C. n the other hand, it is manifest thatshould the resistance of the arcs between A a'ndB -electrodes,

and the bath remain normal, any variation of the current through the electrode C, due to variations in the resistance of its own are, will cause one of the solenoids K or L to exert an orerbalancing pull on the lever M, with the result that electrode C will be either raised or lowered as may be required to increase or decrease the resistance of the are from it. As indicated above, the system above described may be duplicated for the regulation of the other electrodes A and B,

but tnis is not illustrated in detail for the sake of sim )licity.

in the a ovc description of operation I have omitted consideration of the impedance of the system except so far as the resistance of the arcs is com-owed. This simplifies the matter merely notwithstanding that both resistance and inductance in the system as a whole all'ect both the volume and the phase positions of the currents passing between the clectrmles and the bath.

It will be understood that the exact rclatire strengths of the opposing solenoids K and L may be other than those given by way of illustration, and that in many other spearm details the apparatus may be greatly modified without departing from the spirit of the invention, which will now be seen to reside, in essence, in the regulation of each electrode in a poly-phase furnace by two mechanicall) opposed magnetic elements, one energized by the current passing through the electrode to be regulated and tending to adjust the same in a direction to decrease the current f'lmr, and the other partially balancing the attractive effort of the first and energized by the resultant of the currents fiow ing through the other electrodes.

\Vhat, therefore, I now claim as my invention is:

1. The combination with any one of the. of a polyphase electric furnace of regulating means therefor, comprising a magnetic element energizedby the current flowing through the said electrode and when opcratin adapted to decrease the said current, an a partly counterbalancing opposing magnetic element energized by a resultant of the'currents flowing through the other electrodes, asset forth.

- 2. In a polyphase electric furnace, the

- combination with each electrode therein, of

a magnet or solenoid energized by tbecurrent flowing through such electrode and adapted upon the passage through it of an excessive current to reduce such current flow, and a partly counterbalancing opposing magnet energized by a resultant of the currents flowing through the other electrodes, and adapted when operative to orerbalanco the efl'cct of the other magnet to increase the How of current through the first named electrode, as set forth.

3. In a polyphase electric furnace, the combination with each electrode therein, of a magnet or solenoid energized by currents induced from that flowingthrough the said electrode and adapted on a given increase in the energizing current to reduce the flow of current through the electrode, and a. partly.

counter-balancing opposing magnet or solenoid energized by a. resultant of currents induced from those flowing through the other electrodes and adapted when operative to over-balance the efi'ect of the other magnet to increase the current inducing the energizing current of the latter.

4. The combination-with any one of the electrodes in a polyphase. electric furnace, of a solenoid energized by the current flowing through said electrode, a solenoid of normally less attractire power energized b a resultant of the currents flowing through the other electrodes, a mechanical device controlled by the two solenoids and acted upon by means which compensates for the normal difference in the effects thereof, and means controlledby said device for raising and lowering the regulated electrode according to the solenoid which exerts a preponderat-' ing effect.

5. The combination with one of the electrodes, of a polyphase furnace, of a. solenoid energized by current flowing through said electrode, a solenoid of lesser power energizerl by a. resultant of the currents flowing through the other electrodes, :1 pivoted beam oppositely attracted by the two solenoids, a compensating device acting thereon toassist the weaker solenoid to maintain the beam in balance, a circuit controller operated by the movement of the beam, and a motor operated in either direction according to the- 'osition said electrode.

In testimony whereof I aflix'my signature.

JOSEPH L. DIXON.

- of the beam for raising and lowering the 10 

